The global upswing is still young, and has momentum. Mr Trump's policies have lifted the spirits of business leaders, who already had reason to be confident. Galling through it must be to the president's critics, America's economy is well placed for 2018.

【翻译】全球经济仍然处在上升初期，但势头强劲。特朗普的政策鼓舞了商界领袖们的志气，他们已经有理由充满信心。尽管这让总统的批评者们倍感恼怒，但美国2018的经济状况仍然向好。

我认为，你给的这部分句子有误：Galling through it must be to the president's critics, 应该是：Galling though it must be to the president's critics —— 是though 不是through。

那么，这是一个让步状语从句。为了强调，把形容词表语galling（难堪的；恼怒的）提到了though 之前。现还原为：

Though it must be galling to the president's critics, America's economy is well placed for 2018.

翻译见上面黑体部分。

为了理解，我重新paraphrase 这句话：

Though the president's critics must be angry about it, the American economy in 2018 is still in a good position.