NATO countries in Europe are increasing their defence budgets and have been seen the 2014 target of 2% was set. However it should be noted that the actual agreement was to stop the cuts in defense spending, and to gradually increase spending towards the goal of 2% of GDP within a decade.
As for US Forces in Europe, they do not defend Europe, do you really think 30,000 US Troops are going to stop the Russian Army by themselves.
As already pointed out the European NATO Countries spend in the region of $230 Billion, a year collectively and have around 1.8 million military pesonnel and a lot of very modern military equipment.
As for US Bases they are really restricted to a few countries, mainly Germany and Italy, you only find the odd one outside these countries. Indeed in terms of the UK, the US has withdrawn all US Personnal from Fairford and Welford, and is closing Mildenhall, Alconbury and Molesworth.
This leaves Lakenheath as the only active USAF base, and it is designated to operate F-35's alongside the RAF F-35's at nearby Marham. The idea being that the UK and US Forces should operare together in overseas NATO operations, when the new Royal Navy Aircraft Carriers of the Elizabeth Class come in to operation.
US announces first F-35 in Europe to be based in the UK - RAF
Queen Elizabeth Class - Aircraft Carrier Alliance
The other two US Bases in the UK relate to the very secretive NSA/NRO base at Menwith Hill which is directly linked to Fort Meade and the equally secretive base at Croughton which is being expanded, and which is a major communications and intelligence centre.
Other bases that the Americans use include Fylingdales which is an RAF Radar Station linked to the US Ballistic Missile Early Warning System and which has a direct link to the US Base at Cheyenne Mountain Complex in Colarado, and which helps give the US advanced warning of nuclear attack.
Mowenstowe in Cornwall is also a usefu UK/US inteligence hub, as it is the site of numerous cable links between the US and UK, whilst the US also uses RAF Waddington in relation to drones and according to recent report a Joint RC-135 US/UK Rivet John base is to be established, whilst Britain has just ordered 9 Poseidon P-8 Maritime Patrol Aircraft from the US and the British Army has recently confirmed it has started negotiations to procure the Oshkosh Joint Light Tactical Vehicle from the US .
US looks to joint RC-135 base with the UK | IHS Jane's 360
Britain, US pledge to improve cooperation in maritime patrol operations
UK confirms FMS JLTV buy for MRV-P | IHS Jane's 360
MoD orders new fleet of Apache helicopters | Defence Business
It also should be noted that the NATO's Very High Readiness Joint Task Force is now fully operational and Britain which is major contributor to the new force has taken command, with recent joint exercises having taken place.
UK to lead Nato's very high readiness joint task force - Army Technology
Furthermore recent operations in Afghanistan were NATO led, and nearly 1,000 European NATO personnel dies in operations in Afghanistan, with many thoudands injured and the financial cost was also substantial, and this is something Americans should remember when they are critical of NATO.
As for the 2% it is a target that needs to be met over the next few years, and European countries are increasing their defence budgets as a result of the 2014 Agreement with particular reference to Germany which has strong economy and which is where a large percentage of US Forces in Europe are based.