Does it do anything to enhance Russian power to our detriment? Does this signal some new era of Russian expansionism? Is Putin a threat to Europe?
Yes, yes, yes, and yes.
Ukraine is the strategic lynchpin of Eastern Europe. It is the crossroads between Russia, Central Europe, the Black Sea, the Balkans, the Baltics, and the Caucasus. Its destiny has a crucial impact on the destiny of all those regions, and the reason that hasn't been more apparent in recent years is because Ukraine has still been reeling from the breakup of the Soviet Union and has remained tenuously in Russia's orbit.
Ukraine has the potential to be a force of stability and modernity or of disruption and antagonism. Russia desperately wants to reabsorb Ukraine thereby amplifying its influence dramatically once again in the Balkans and Central Europe. A hostile Russia in the future with Ukraine could easily rekindle the Cold War in the midst of Europe. A hostile Russia without Ukraine would be hemmed in, and even more so if Belarus is eventually pried from its clutches.
The progress of Ukraine also has a substantial impact on free market and free society reforms in Russia and the rest of the former Soviet Union. A slide back toward an authoritarian satellite-state would not only expand Russia's geopolitical power but would also consolidate similar reactionary developments there. There is nothing trivial about the future of Ukraine, except that it was under the Russian boot for so long that most Americans don't have the independent historical background to appreciate its critical importance.
Kiev was even rebuilt by the Tsars.
Ukrainian territory is home to a vast array of gazoducts and pipelines, so these resources can go from the Caucasus to Western European ports, and from that, to the ports of Russian customers - of which, IIRC, the USA is and will continue to be a member.