Currency values follow interest rate differentials. When US rates rise relative to Eurozone rates, capital flows into dollars seeking higher yield, and the dollar strengthens against the euro.
Over 25 years, the USD/EUR rate has been strongly influenced by Fed vs ECB policy divergence. The 2015-2020 period of Fed tightening while ECB stayed negative pushed EUR down from 1.39 to 1.04. Post-2022 Fed aggressive hikes while ECB lagged caused similar divergence.
For Americans: stronger dollar makes European travel cheaper and imported goods cheaper, but hurts US exporters and companies with European revenue (they translate fewer dollars from each euro). For investors: a strong dollar typically drags on S&P 500 earnings since ~40% of revenue comes from overseas.