The second boer war takes place with entirely different international domestic political and military context. The UK had a small professional force that it needed to husband not a large force of conscripts that enabled it to send troops to Africa without fear and firearms that let them be useful together with the means to supply them.

No conscription in British army of the Boer War era. I believe conscription for the British army was an innovation that came into being during the First World War.

Modern conscription was an innovation of the First World War, though the militia (restricted to domestic employment, AFAIK) had conscription to fill units in the 18th to early 19th Century.

And in any case, I misread parent comment.

So I don't really know the history but I thought British Army planned on mass call-ups either voluntary and then if needed by conscription long before WWI, as mass mobilization isn't something you can do overnight without prep.

I believe Lord Kitchener campaigned for this in WWI until it became clear to the government at large that sustaining an army appropriate to the struggle they had entered was going to be an order more difficult than envisaged.

You are contrasting the Revolutionary War against a war a century later.

The ability to muster, transport, and support that many troops depends upon modern industrialization.

Maintaining war against the Americans in the late 1700s was brutally expensive for Britain--with minimal ability to recover the costs after they "won". And this isn't even considering the fact that being part of the British army and navy was horrifically terrible--deserting to the American side was almost always an improvement unless you were an officer.

If France and Spain hadn't been present in North America, Britain might have just told the colonies to sod off rather than fight a war.

They landed 32,000 men at New York, the largest British fleet ever assembled up to that point. The idea that they were playing on easy mode is a delusion.

Considering what happened in 1815 I think the British just didn't care all that much. When the US made claims on Canada that changed.

The British also learned from their American experience. The beginnings of something akin to the American revolution were stirring in what are now Ontario and Quebec in the 1830s, culminating in armed rebellion in 1837, with the more radical calling for a republic. The British response was largely conciliatory. The local legislatures would be partially elected, the government responsible to the elected house, and given jurisdiction over issues like taxation, along with a promise that future constitutional changes would only be made with local consultation.

Of course, the USA would have been able and perhaps willing to assist a new Republic of Canada, probably with an eye to absorbing it one day. The British were not in a position to be heavyhanded. It worked though; the King still rules in Canada to this day. One of the great what ifs of history, one of the more plausible ones, I think, is what if the British government had realized they would lose, and had quickly made concessions to the Americans 50 years before?