For the US, a study was conducted on this showing the industry provides a lot more funding than government: https://pmc.ncbi.nlm.nih.gov/articles/PMC10349341/

In this cross-sectional study, phased clinical trials of 387 drugs approved between 2010 and 2019 were associated with $8.1 billion of National Institutes of Health (NIH) funding, primarily for clinical research. This amount represents 3.3% of total NIH funding for basic or applied research related to these products and 9.8% to 10.7% of estimated industry costs, including less than 26% of phase 1 or 2 trials and less than 5% of phase 3 trials.

The findings suggest that NIH spending on clinical development focuses on early-stage trials, representing a small fraction of estimated industry spending.

And if we look at the UK, NHS spent 453.56 Pounds on all research in 2024 (Annual Report: https://www.nihr.ac.uk/nihr-annual-report-202223), a tiny amount compared to the US, even without taking the huge inflation issues into account, meaning the US is driving that development.

"Couldn't exist" is fair to call out, though, I should have said "in their current form". I mention taxes would have to increase to cover the costs, but I may not have been clear enough.