It has been well known for at least the past six decades that Western countries (incl. Japan/Australia/New Zealand, but in particular European countries) have spent too little on their militaries. Essentially, these countries left most of the burden to the US to provide a credible security umbrella and deterrent. This has been a long simmering bone of contention between the US versus other Western countries.
President Trump is right to demand change and more commitment by other Western countries. For as long as Putin the Terrible is still in power and China does not reduce its hegemonic posture, the West has little choice, but to respond.
In addition, the US needs to focus more on the Pacific region, Latin America and Africa to counter China compared to the North Atlantic region. Thus, e.g. European countries need to do more about defending Greenland and the Arctic region as the Arctic region becomes more navigable thanks to global warming. Hint: The US offered to buy/annex Greenland.
Food for thought!
How about a EDTO (European Defense Treaty Organisation) with the US and Canada as close allies of the collective, mutual defense agreement, but not required to automatically become involved in case of an attack on one member (NATO Article 5).
One benefit, Ukraine could join EDTO without upsetting Russia (Putin the Terrible) too much! 😊
Another major benefit, Europe assumes more responsibility for its defense!
