Mortgages are (almost) always 30 years duration.
I don't know what country in Europe you can't get fixed rates but it's not the Netherlands, that I know for sure. (Also there really isn't a 'Europe' for these things, every country is different)
In the United States we don't call that "fixed". We call that an adjustable rate mortgage. For example, my mortgage is fixed at 3% for its entire 30 year term and can properly be called "fixed".
People in the United States are leery of ARMs after what happened during the mortgage crisis in 2006-2011 so proper labeling is more important.
I could also have picked 30 years for a 'real' fixed mortgage. It just gets a bit more expensive. But it's definitely possible to get 30 year fixed if you really want to, every bank offers it.
In the Netherlands an 'adjustable rate mortgage' means monthly, quarterly or yearly variable rates.
Canada is similar to the UK - you amortize (pay back) the loan over 25-30 years. However, your mortgage is either variable (interest rate floats over time) or fixed (interest rate does change), but the loans are only for 1 to 5 years. At the end, you either "renew" your mortgage with the same lender or you "refinance" entirely.
So you can have a "fixed" mortgage, but not for the entire amortization period. But you're correct, it's more similar to the ARM mortgages in the US (potentially fixed for 5-10 years, then floating after).