The GDP per capita in the US is (85k USD) and in Germany (54k USD) nominal. That’s about 57% higher. At PPP (purchase power parity) 85k US vs 67k Germany, which “only” is a 27% difference.
Denmark rates at 68k / 77k. So much closer. Norway is tricky to compare and Netherlands, Ireland and Switzerland are tax havens.
The population of Denmark is equal to that of Wisconsin. If we look at Denmark simply because it's among the richest EU countries, it might be more appropriate to compare it with the richest US states. Taking the top 5 state (California), we get $100k vs $68k (nominal), again ca 50%.
These estimates are really approximate and depend on the exchange rate. The lowest rate of NOK/USD on my memory was 5.6 and the highest nearly 12.
Developer salaries in Norway are decent as Europe goes but if you want to make money hand over fist there's no other place like America. Yes even with all the old world perks imaginable.
https://en.wikipedia.org/wiki/List_of_U.S._states_and_territ...