US GDP is about $21T, so about 420 times bigger. Or to put it differently, about 0.2% of the GDP.
Also, wage theft isn't fraud exactly.
UK has a massive problem with phone scams pretending to be tech support or our tax office for example. They get victims to wire money to the account of a money mule who then cashes it out. This all happens over the normal banking system - enforcement is so bad that they're not even trying to cover their tracks by using gift cards or crypto.
How does that compare to UK's GDP, for the problem to be massive?