By Maria Santana, Steve Almasy and Theresa Waldrop, CNN

(CNN) -- A former US Army soldier whose felony conviction led to the revocation of his green card, his imprisonment, and, just days ago, his deportation to Mexico, said he will fight what he calls the unjust treatment of immigrant veterans.

"I belong in the (United States)," Miguel Perez, who came to the US legally as a child and served two tours in Afghanistan, told CNN.

And if he were to get back to the US and was called to return to the military, Perez said that even after all the stress his service and deportation created, he would re-enlist in a second.

"Right now. Right now I would go," he said. "For the (American) people."

His deportation follows a decision by US authorities to deny Perez's citizenship application because of a 2010 felony drug conviction, despite his military service.

Perez, 39, said he was trying to help a friend by delivering a bag and picking up a package when he was arrested in a drug sting.

He served half of a 15-year sentence and had been in the custody of US Immigration and Customs Enforcement since 2016.

On Friday he was deported to Mexico, and Tuesday in Tijuana, he spoke to the media.

"I will continue to struggle, not only for myself, but for other veterans and others who have been separated from their families by the US's unjust immigration laws. It is my duty to continue this fight for equity," he said at a news conference before he gave an exclusive television interview to CNN.

Perez told CNN that doing 7 1/2 years in prison and then being deported for a non-violent felony amounts to double jeopardy -- being punished twice for the same crime.

Not a victim but a witness, he says

Perez said he was not treated during his service during which he said he suffered brain injuries and developed Post Traumatic Stress Disorder after he was discharged. He developed a drug addiction and made a bad decision to hang out with an old friend, one who was being followed by federal drug agents.

He said he committed a crime but really wasn't a criminal -- and took responsibility for his crime.

He said he got no support for his PTSD and little support from Veterans Affairs after he was discharged.

But while in prison, he said he received medication, and "day by day I got myself together, studying and increasing in my faith."

And then he was turned over to ICE.

"I am not a victim -- but I am a witness to the policies of mass incarceration and mass deportation. I am not a victim, but I am a witness to the way veterans are treated, disrespected and thrown away after they sacrificed for the nation," he said.

He doesn't blame the government per se; it's the people in power now that hide behind the word government, he told CNN.

Border door closes on him

Perez said he didn't realize he'd been deported to Mexico until it was too late to turn back.

He was escorted across the US-Mexico border from Texas and handed over to Mexican authorities Friday, ICE said in a statement.

Perez said a truck took him to an airport in Indiana. He was then flown to Brownsville, Texas, ICE said.

When he got off the plane, Perez said was bussed to a place that looked like a detention center.

He told CNN he did not know he was at the bridge that went to Matamoros, Mexico. He walked through a gate that closed quickly behind him.

A federal agent he had been making small talk with, told him, "OK, we're done here. ... You see those two green arrows, that's Mexico. Go ask them for help."

Perez said he briefly thought about jumping off the bridge over the Rio Grande and killing himself. But by the time he got to the other side he had regained his composure.

Senator: Perez kicked out without due process

Perez was born in Mexico and came to the United States at age 8 when his father, Miguel Perez Sr., a semi-pro soccer player, moved the family to Chicago because of a job offer, Perez told CNN earlier.

He has two children born in the United States -- a daughter who is 20 and a son who is 10. The son still thinks he is in ICE custody, Perez believes.

His parents and one sister are now naturalized American citizens, and another sister is an American citizen by birth.

It's a complicated case. Perez has said that what he saw and experienced in Afghanistan sent his life off the rails, leading to heavy drinking, a drug addiction and ultimately to his felony conviction.

"After the second tour, there was more alcohol and that was also when I tried some drugs," Perez said last month. "But the addiction really started after I got back to Chicago, when I got back home, because I did not feel very sociable."

In 2010, he was convicted in Cook County, Illinois, on charges related to delivering more than 2 pounds of cocaine to an undercover officer. He was sentenced to 15 years and his green card was revoked.

Perez has said he was surprised to be in ICE detention and mistakenly believed that enlisting in the Army would automatically give him US citizenship, according to his lawyer, Chris Bergin. His retroactive application for citizenship was denied earlier this month. While there are provisions for expediting troops' naturalization process, a main requirement is that the applicant demonstrate "good moral character," and the drug conviction was enough to sway the decision against his application, Bergin said.

Perez enlisted in the Army in 2001, just months before 9/11. He served in Afghanistan from October 2002 to April 2003 and again from May to October 2003, according to his lawyer. He left the Army in 2004 with a general discharge after he was caught smoking marijuana on base.

Perez went on a hunger strike earlier this year, saying he feared deportation would mean death. Aside from not getting the treatment he needs, he told CNN that he fears Mexican drug cartels will try to recruit him because of his combat experience and will murder him if he doesn't cooperate.

When he got to Mexico the first person he met outside the detention center where he got his temporary ID made him uneasy. The guy said to him, "You've been in prison, yeah you did." The man told Perez to come with him and others.

"We got you," the man, who Perez thinks was a cartel member, said.

Perez went back to the detention center and made some calls. Friends and family hurriedly came a few days later from the US.

But they have to go back soon, and he'll have to leave the hotel that others have paid for.

He'll be basically homeless with only a $60 on a cash card.

But worse, his PTSD medicine will run out within 10 days and he has had no idea how he will get more.

He's worried because he still has anxiety and night terrors.

He will be alone, fretting that if he reaches out to relatives in Mexico he will put them in danger with the cartels and also put them in a position where they have to care for a scarred veteran.

"I'm taking it a minute at a time," he told CNN. He hopes to get back to the United States but knows it's a longshot that could take a long time.