In US lingo, that would be referred to as an adjustable rate, like "5/1 ARM" (fixed for five years, then adjusts each [one] year). When they say "fixed" in the US, they mean fixed for the full term.

I'm honestly surprised that became the standard, it seems like a lot of risks for the banks for what they're getting. I think it has something to do with Fannie Mae and Freddie Mac preferring to buy some mortgages and absorb the risk?

https://www.bankrate.com/glossary/0-9/7-1-arm/