The EU average is about the same as Canada at 13.7% of GDP. The UK is up at 19.2%. If anything, I would think that Canada's 2020 deficit is pretty typical of developed countries.
A currency’s value is the trust that you will be able to exchange it in the future for something you want.
An army can help that by signaling the stability of the country. An army alone does not do the job though, the real value lies in the trust and organization of the society itself. The more of that there is, the more others will believe the currency will be able to buy something they want, since organized societies with high trust are able to produce desirable things.
A secondary concern an army helps with is enforcing laws and preventing fraud, such as counterfeiting. If you know the US is not going to let some other tribe or country counterfeit their country, and has the capability to stop them, it helps you trust the currency more.
Obviously, the armed forces aren’t directly involved in the first few layers of conflict, but it’s always advantageous to have the ability to park an aircraft carrier fleet off someone’s coast during negotiations.
The largest producer (Saudi Arabia and other OPEC members) of crude will only accept USD for payment. In exchange the US guarantees security. You may read the inverse of the security guarantee as well. Producers defying the arrangement may expect regime change or other hostilities.
>However, by 1971, convertibility into gold was no longer viable as America's gold resources drained away. Instead, the dollar became a pure fiat currency (decoupled from any physical store of value), until the Petrodollar Agreement was concluded by President Richard Nixon and Secretary of State Henry Kissinger in 1973.
The essence of the deal was that the U.S. would agree to military sales and defence of Saudi Arabia in return for all oil trade being denominated in U.S. Dollars. A secondary option to this agreement is the purchase of U.S. debt securities with surplus oil proceeds. By 1975, all OPEC nations agreed to price their oil supplies exclusively in U.S. Dollars and to hold their oil proceeds in U.S. government debt securities.
The graph is for the growth of debt to GDP - we previously had lower debt and so the need to react to COVID caused the debt to grow by quite a bit as CERB was implemented to try and keep people liquid. I can't find any break downs of 2020 in terms of actual debt to GDP, but the chart supplied definitely isn't telling the whole story.
Canada's deficit is among the worst of all relevant countries at the moment.