The weakness President Biden demonstrated in the Middle East over Afghanistan was unfortunate. It should not be repeated elsewhere. The President wanted to be closer to allies but has instead upset them by his unilateral and unwise decision. That is all the more reason for him now to draw closer in other places where alliances are important.
In Korea the USA still maintains a substantial military presence to support the South Korean forces. North Korea with its erratic autocrat in charge needs to know that the USA continues with her long term commitment to support the South. So does China need to understand that trying to control her wayward neighbouring state.
President Biden has in the past made clear he will support Taiwan. He will need to do so again, and be ready to respond to any further tests of resolve from Chinese naval vessels and planes coming close to the island. NATO as a whole is engaged, with naval vessels from other NATO countries assisting the USA in keeping open international waters in the South China Sea.
In eastern Europe NATO has forces in the Baltic Republics as a reminder to Russia that they have chosen to be allies of the West. US rapid reaction forces are an important part of the NATO support.
The world has just got even more dangerous with the collapse of the Afghan government and the release of prisoners from Afghan jails. Counter terrorism is a daily task for many years, not something democratic countries can get bored with or pretend the need has gone away. There are regular challenges to western defences by conventional weapons and by many cyber probes and assaults. Some come from rogue states or from terrorist groups. Some are tolerated if not directed by large states that the West has to do business with. This requires clear leadership, defining lines of conduct and imposing sanctions or responding as needed where lines are crossed. After Afghanistan President Biden will have to be tougher and clearer to avoid more disasters elsewhere. UK diplomacy could help rebuild trust between the USA and the allies, assuming President Biden recognises the need to reassert US leadership against violent and unacceptable conduct.