A Canadian woman is once again the face of U.S. political attack ads, saying that Canada's medical system failed her and she would have died if she hadn't sought help south of the border.

The new ad is paid for by the pro-Republican group Americans for Prosperity and is meant to serve as a warning against Democratic U.S. President Barack Obama's attempts to bring universal health care to America. The ads were launched just weeks before the U.S. presidential election on Nov. 6.

Shona Holmes describes in the sombre ad how she began to experience vision problems, and was told she would have to wait up to six months to see a specialist.

The Waterdown, Ont. woman and her husband then travelled to the Mayo Clinic in Arizona for help.

"The (U.S.) doctors agreed that they would do anything that they could in order to get me in for treatment back at home in Canada," Holmes says in the ad. "My husband spoke up and said 'We have an appointment in September.' And the doctor put down his pen and said, 'Your wife will be dead in September.'"

Holmes says she realized then just how "dangerous for patients" the Canadian system had become, and made the decision to get help at the Mayo Clinic for what turned out to be a growth on her brain.

Holmes re-mortgaged her home in order to afford her U.S. treatment, which cost about $100,000.

"The American system was there for me when I needed it and it's time for Americans to get engaged in this debate," she says in the ad.

The commercial ends with the voice-over warning: "To protect America's patient-centred care we must replace President Obama."

Holmes first made headlines in 2009 when she became a spokesperson for a campaign by the Center for Medicine in the Public Interest's BigGovHealth campaign.

That campaign also warned that if Holmes had waited for treatment in Canada, she would have died. However, media reports later cited experts who said Holmes' growth was a benign, non-life threatening cyst, and a six-month delay in treatment was reasonable under the circumstances.

The ad, which ran in 50 states, was sponsored by Patients United Now, a citizens' group that opposes government-run health care.

The ad claimed that Canadians wait a long time for care and are denied care or cannot access some drugs or treatments, "because the government says patients aren't worth it."

At the time Holmes defended her appearance in the ad, saying she wanted to warn both Canadians and Americans, tens of millions of whom do not have health insurance, that many patients in Canada are falling through the cracks.

Obama wants to overhaul the American health care system and expand coverage to the roughly 50 million Americans who do not have insurance.

He has faced opposition from both Democrats and Republicans over the controversial move.